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Sorry, seems I forgot to say that the current domain is a .com...

A company located in Canada is currently targeting Canada through the geotargeting setting in Google Webmaster Tools.  Google.ca rankings are good, but Google.com rankings are not. The company would like to gain more traction for US people using google.com.

The idea on the table is to set up a subfolder www.domain.com/us/ and use WMT to designate this version for the US.

Here's the kicker:  the content is exactly the same.

Will Google consider the US version duplicate content?  Is this an effective way to target US and Canada at the same time? Is it better to forget a duplicate US site altogether and use the "unlisted" setting in WMT?

It's a niche business so the terms are fairly unique and not extremely competitive. Client is probably asking the wrong question.  It's not that his places page is hurting his national ranking, it's that his location is helping his local rankings.  Don't ya think?

A client with both a web and brick and mortar store is ranking well for normal web searches locally for many terms but less so nationally. I'm aware that results change due to location and other factors. Specifically, client is wondering if his retail location and corresponding places page are hurting his web results in non-local areas.